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Single (TiO2) and complex (TiO2 and ZrO2) nucleating agents were added in CaO–Al2O3–SiO2–ZnO–Na2O–K2O‐based multicomponent glass to investigate its crystallization behavior and physical properties according to the types and amounts of nucleating agents. Nonisothermal analysis revealed crystallization behavior with an activation energy (E) of 165.176–518.985 kJ/mol and Avrami constant (n) of.73–2.12 with the complex nucleating agent. X‐ray diffraction was used to observe the titanite and zircon crystalline phases in glass when using complex nucleating agents, and the crystallinity was found to be 43%–55%. Scanning electron microscopy and energy‐dispersive x‐ray spectroscopy were used to observe the plate‐shaped titanite and column‐shaped zircon crystalline phase in the glass matrix, and the glossiness was found to be decreased owing to the crystallization of the glass. The glass‐ceramic showed a higher hardness and fracture toughness value of 6.45–6.7 GPa and 1.54–3.35 MPa∙m1/2 when using the complex nucleating agent rather than when using the single nucleating agent. [ABSTRACT FROM AUTHOR]

MgO was added to the SiO2-Al2O3-CaO-ZrO2-based glaze to produce a high-hardness glaze by forming a composite crystal phase. The effects of MgO addition on the surface properties of the glaze were analyzed through crystal phase and microstructural investigations, and the whiteness, roughness, gloss, wear rate, and hardness were measured. When the amount of added MgO increased by 2.20 wt% or more, the diopside (MgCaSi2O6) crystal phase was observed via X-ray diffraction (XRD) and scanning electron microscopy (SEM), in addition to the zircon (ZrSiO4) crystal phase. All samples exhibited high whiteness and the surface roughness increased with increasing MgO content. At the same time, the gloss decreased significantly, resulting in a matte. The Vickers hardness test results of the glazed surface indicated high hardness values of 6.23–7.07 GPa with increased amounts of MgO. [ABSTRACT FROM AUTHOR]

In this study, waste silica fume was used as the raw material for manufacturing porous ceramics, and its mechanical and thermal properties required for application as thermal insulators were studied. For pore formation with direct foaming, Si sludge (0.01, 0.05, and 0.1 wt%) and NaOH aqueous solution (14 N) were used as the foaming agents. The porous ceramics sintered at 900°C showed an apparent porosity of 85.9–89.8%, and the specimen with 0.1 wt% Si sludge showed the highest apparent porosity of 89.8% and a bulk density of 0.24 g/cm3. Scanning electron microscopy results showed that with increasing Si sludge substitution, an open pore structure was formed because of the increase in the pore size from several tens to several hundreds of micrometers. The compressive strength decreased from 3.82 to 2.11 MPa as the amount of added Si sludge increased from 0.01 to 0.1%, respectively. The thermal conductivity was less than 1.0 W·m−1·K−1 in the temperature range of 25–800°C, and the specimen with 0.1 wt% Si sludge showed a low thermal conductivity of 0.2–0.6 W·m−1·K−1. The thermal expansion coefficients were 17.1–22.4 × 10−6/K in the temperature range of 25–800°C. [ABSTRACT FROM AUTHOR]